You need a 25% alcohol solution. On hand, you have a 75 mL of a 90% alcohol mixture. How much pure water will you need to add to obtain the desired solution? You will need mL of pure water to obtain mL of the desired 25% solution.

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Answer 1 · 2018-03-12T17:27:11

Added water # 195.4ml# to obtain #270.4ml# of 25% solution

Let the amount of the final blend be #x#

Note that the alcohol content of the water is 0

The amount of alcohol in the 90% mix is #90/100xx75ml= 67.6ml#

The final blend is to be a 25% solution

#67.6/x=25/100#

Turn everything upside down

#x/67.6=cancel(100)^4/cancel(25)^1#

#x=4xx67.6 = 270.4 ml larr" Final blend volume"#

Added water #270.4-75 = 195.4ml#
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#color(blue)("Check")#

#67.6/270.4 xx100= 25%#

You need a 25% alcohol solution. On hand, you have a 75 mL of a 90% alcohol mixture. How much pure water will you need to add to obtain the desired solution? You will need __ mL of pure water to obtain __mL of the desired 25% solution.